Performance requirements of the hottest integrated

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Performance requirements of the integrated multivariable hwbh balance flowmeter

the integrated multivariable hwbh balance flowmeter is a new type of instrument, which is easy to use and deeply loved by the majority of users. Its performance requirements are as follows:

I. response time

when applied to pulsating flow occasions, attention should be paid to the response of the flowmeter to the flow step change. Some applications require the flowmeter output to follow the fluid flow, while others require a slower response output to obtain a comprehensive average value. The instantaneous response is often expressed in terms of time constant or response frequency. The former ranges from a few milliseconds to a few seconds, while the latter ranges below hundreds of Hz. The response time may be considerably prolonged by the use of display instruments. It is generally believed that the asymmetric dynamic response will accelerate the increase of flow measurement error when the flow of the flowmeter increases or decreases

II. Repeatability

repeatability is determined by the principle and manufacturing quality of the flowmeter. It is an important technical index in the use of the flowmeter and is closely related to the accuracy of the flowmeter. Generally, in the metrological performance requirements in the verification regulation, the flowmeter has not only the accuracy grade, but also the repeatability, which is generally specified as: the repeatability of the flowmeter shall not exceed 1/3-1/5 of the maximum allowable error specified in the corresponding accuracy grade

repeatability is generally defined as the consistency of multiple measurements in the same direction for a certain flow value in a short time under constant environmental conditions and medium parameters. However, in practical application, the repeatability of the flowmeter is often affected by the changes of fluid viscosity and density parameters. Sometimes these parameters do not change to the extent that they need to be specially corrected, which may be mistaken for the poor repeatability of the flowmeter. In this case, the integrated multivariable hwbh balance flowmeter which is insensitive to the change of this parameter should be selected

III. flow measurement or total amount

flow measurement includes two types, namely, instantaneous flow and cumulative flow. For example, the total amount needs to be measured for the crude oil in the off load station pipeline belongs to trade handover or the process control of continuous proportioning production or production process in the petrochemical pipeline, sometimes supplemented by the observation of instantaneous flow. Instantaneous flow measurement is required for flow control in some workplaces. Therefore, it should be selected according to the needs of on-site measurement. Some flow meters, such as positive displacement flow meters and turbine flow meters, are based on the principle of mechanical counting or pulse frequency output to directly obtain the total amount. They have high accuracy and are suitable for measuring the total amount. If they are equipped with corresponding sending devices, they can also output the flow. Electromagnetic flowmeter, ultrasonic flowmeter, etc. derive the flow by measuring the fluid flow rate, which has fast response and is suitable for process control. If equipped with the integration function, the total amount can also be obtained

IV. accuracy

the accuracy grade of flowmeter is specified within a certain flow range. If it is used under a specific condition or within a relatively narrow flow range, for example, it changes only within a very small range, then its measurement accuracy will be higher than the specified accuracy grade. If the turbine flowmeter is used to measure the distribution of oil in barrels, when the valve is fully open, the flow is basically constant, and its accuracy may be improved from 0.5 to 0.25

the accuracy grade is generally determined according to the maximum allowable error of the integrated multivariable hwbh balance flowmeter. It will be given in the flowmeter instructions provided by each manufacturer. It must be noted that the percentage of error refers to relative error or reference error. The relative error is the percentage of the measured value, usually expressed as "%r". The reference error refers to the percentage of the upper limit value or measuring range, which is commonly used as "%fs". Many manufacturers do not specify this in their instructions. For example, the float flowmeter generally adopts reference error, and some models of electromagnetic flowmeter also adopt reference error

v. linearity

the output of flowmeter mainly includes linear and nonlinear square root. Generally speaking, the non-linear error of flowmeter is not listed separately, but included in the error of flowmeter. For the flowmeter with a wide flow range and pulse output signal, which is used as the total amount integration, the linearity is an important technical index. If a single instrument coefficient is used within its flow range, the accuracy of the flowmeter will be reduced when the linearity difference. For example, the turbine flowmeter adopts an instrument coefficient in the flow range of 10:1, and its accuracy will be low when the linearity is poor. With the development of computer technology, its flow range can be segmented, and the flow instrument coefficient curve can be fitted by the least square method to correct the flowmeter, so as to improve the accuracy of the flowmeter and expand the flow range

VI. pressure loss

pressure loss generally refers to the unrecoverable pressure loss that changes with the flow due to the static or movable detection element set in the flow channel or the change of flow direction of the flow sensor, and its value can sometimes reach tens of kPa. Therefore, the most integrated flowmeter shall be determined according to the pumping capacity of the pipeline system and the inlet pressure of the flowmeter. 1. Before the use of the experimental machine, check the connection of power supply, wires and equipment. The variable hwbh balances the allowable pressure loss of the flowmeter to select the flowmeter. Improper selection will restrict the fluid flow and cause excessive pressure loss, which will affect the flow efficiency. For some liquids (high steam 4. remote sensing and remote sensing of vapor pressure hydrocarbon liquid) it should also be noted that excessive pressure drop may cause cavitation and liquid vaporization, reduce measurement accuracy and even damage the flowmeter. For example, for the flowmeter used for water transmission with a pipe diameter greater than 500mm, the increased pumping cost due to excessive energy loss caused by pressure loss shall be considered to shorten the moving distance of the melt as far as possible. According to relevant reports, the pumping cost of flowmeter with large pressure loss for measurement in recent years often exceeds the purchase cost of flowmeter with low pressure loss and high price

VII. Upper limit flow and flow range

upper limit flow is also called the full flow or maximum flow of the flowmeter. When we select the diameter of the flowmeter, we should configure it according to the flow range used by the tested pipeline and the upper and lower limit flow of the selected flowmeter. We cannot simply configure it according to the pipe diameter

generally speaking, the maximum flow rate of design pipeline fluid is determined according to the economic flow rate. If the selection is too low and the pipe diameter is too large, the investment will be large; If the transmission power is too high, the operation cost will be increased. For example, the economic flow rate of low viscosity liquid such as water is 1.5. The operator 1 must pay attention to the cleaning of fatigue testing machine - 3m/s, and the high viscosity liquid is 0.2 - 1m/s. The upper limit flow rate of most flow meters is close to or higher than the economic flow rate of the pipeline. Therefore, when the flowmeter is selected, its diameter is more when it is the same as that of the pipeline, and the installation is more convenient. If they are different, there will not be too much difference. Generally, the specifications of the upper and lower adjacent gears can be connected by reducer

VIII. Output signal characteristics

the output and display quantity of flowmeter can be divided into:

1, flow (volume flow or mass flow)

2, total amount

3, average flow velocity

4, point velocity. Some flow meters output analog quantity (current or voltage), while others output pulse quantity. Analog output is generally considered to be suitable for process control, and is more suitable for connection with control loop units such as regulating valves; Pulse output is more suitable for total volume and high accuracy flow measurement. Long distance signal transmission pulse output has higher transmission accuracy than analog output. The mode and amplitude of output signal shall also have the ability to adapt to other equipment, such as control interface, data processor, alarm device, open circuit protection circuit and data transmission system

IX. range degree

range degree is the ratio of upper limit flow and lower limit flow of the integrated multivariable hwbh balance flowmeter. The larger the value, the wider the flow range. Linear instruments have a wide range, generally 1:10. The range of nonlinear flowmeter is only 1:3. Generally used for process control or trade handover accounting, if the flow range is required to be wide, do not choose a flowmeter with a small range

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